Physical origins of current and temperature controlled negative differential resistances in NbO2

Abstract

Negative differential resistance behavior in oxide memristors, especially those using NbO2, is gaining renewed interest because of its potential utility in neuromorphic computing. However, there has been a decade-long controversy over whether the negative differential resistance is caused by a relatively low-temperature non-linear transport mechanism or a high-temperature Mott transition. Resolving this issue will enable consistent and robust predictive modeling of this phenomenon for different applications. Here we examine NbO2 memristors that exhibit both a current-controlled and a temperature-controlled negative differential resistance. Through thermal and chemical spectromicroscopy and numerical simulations, we confirm that the former is caused by a ~400 K non-linear-transport-driven instability and the latter is caused by the ~1000 K Mott metal-insulator transition, for which the thermal conductance counter-intuitively decreases in the metallic state relative to the insulating state.

Origin of Current‐Controlled Negative Differential Resistance Modes and the Emergence of Composite Characteristics with High Complexity

“…3b. The onset temperature in this case is predicted to be ~450 K, consistent with simulations based on Poole-Frenkel conduction 22 and experimental observations 25 . The counter example is shown if Fig.…”

“…While the above studies provide a foundation for understanding S-type NDR characteristics, they do not explain the diverse range of other NDR characteristics exhibited by thin film oxides, such as the discontinuous snap-back response observed in oxides such as NbOx 25 , TaOx 26 , SiOx 27 . This is analogous to a similar response observed in chalcogenide glasses 28 and is characterised by abrupt, hysteretic voltage changes during bidirectional current sweeps.…”

Memristive Synapses and Neurons for Bioinspired Computing

“…In a VCM cell, resistive switching is generally attributed to the creation/ annihilation of oxygen-deficient conductive filaments based on oxygen migration. [146][147][148][149][150][151] Adv. [104][105][106][107] In addition, electronic memristive devices, in which the resistive switching is attributed to a purely electronic process, have internal advantages in terms of switching uniformity and reliability.…”

S‐Type Negative Differential Resistance in Semiconducting Transition‐Metal Dichalcogenides

“…[4,26] Therefore, it is quite desirable to expand the material matrix hosting the stable S-type NDR based on this new and simple mechanism. Unfortunately, its experimental observation has been limited to the NbO x system so far.…”

“…For instance, selector based on S-type NDR can limit the leakage current in memristor cross-bar arrays due to highly nonlinear I-V characteristics. On the other hand, a recently proposed thermal feedback mechanism , [4,26,27] in which only temperature dependence of material conductivity and Joule self-heating effect at large currents are involved, is a very promising approach for generating www.advelectronicmat.de until the dielectric layers (MoS 2 , WS 2 , and WSe 2 ) are broken down under the large electric field and high temperature generated by the applied voltage and current. [5,6] Most of reported S-type NDR result from distinct properties of materials, such as electronic instabilities, [7,8] interband tunneling, [9,10] threshold switching, [11][12][13] insulator-metal transitions in metal oxides.…”